Add an addon to a subscription with auto_collect set to false

Add an addon to a subscription with auto_collect set to false

Hi,

I would like to add an addon to an existing subscription 
( https://www.zoho.com/subscriptions/api/v1/#Subscriptions_Update_a_subscription).

I have set auto_collect to false but the API answers

{"code":8006,"message":"La carte n’est pas spécifiée. Veuillez ajouter une carte à cet abonnement pour continuer."}

Is there an issue in the API ?

Thanks for your replies.